Biggest name and best grappler are two different things ofcourse. If you are asking for biggest name, I rolled with Dan Hardy as he spent some time in our school. I actually did great but was suprised how strong he was for his size. My coaches are probably a hundred times better than him and crush me in to a paste on a daily basis, however thay are not household names.
For me, excluding my instructor Gerald, its eddie and denny. I didn't stand a chance with either. I've rolled wth other good guys just no name recognition yet.
Royce Gracie, and I got my ass taken to school, and he was probably going 10% lol. But I was only a month into training so I was pretty much star struck the whole time.